This invention the counting of a plurality of small parts. The invention is especially useful in packing measured quantities of similar parts for distribution and sale.
It has been known, in the prior art, to count articles, or "parts", automatically prior to packaging them. U.S. Pat. No. 3,618,819 discloses a typical counting device of the prior art. The disclosure of the latter patent is incorporated by reference herein. The device shown in the patent accepts parts from a feeder, and accumulates batches of parts until the correct number has been detected. The device is then programmed to dump the batch of parts into a bag, or other suitable container, for eventual sale.
The device shown in the cited patent employs a solar cell which generates a current when light shines upon it. The parts are made to pass between the solar cell and a source of light. When the part blocks all or some of the light entering the solar cell, the current through the cell decreases. The apparatus detects the change in this current, and produces a pulse which can be counted as a part. When the desired number of parts have been accumulated, the device operates a deflector to prevent further parts from entering, and also operates a trap door to allow the counted batch of parts to fall into a container.
Various factors prevent the accurate counting of parts, in the counters of the prior art. Depending on the length and shape of the parts, a counter may interpret a single part as two parts, or it may interpret a group of several parts as one part. To the extent that the device detects more parts than are actually present, the number of parts in a package will be too small. The counters of the prior art have been programmed to compensate for these errors. But a consequence of such compensation is that many containers will contain more parts than necessary. Thus, compensation for inaccurate counting can be very costly, because customers receive more product than necessary.
The present invention provides an electronic counting circuit which solves the above-described problem, and which has various other features and advantages. With the present invention, it is possible to adjust the counter to take into consideration the length and/or shape of the parts being counted, so as to reduce the likelihood of inaccurate counting. The invention also provides for the automatic setting of values used by the system, through analysis of the actual parts to be counted. The invention also includes means for determining whether the wrong kind of part has been mixed with the parts being counted, as well as circuitry for performing diagnostic checks substantially simultaneously with the counting operation.